Service insertion architecture (SIA) provides a platform-independent framework for service virtualization and dynamic service insertion into a network. An example SIA is described and claimed in U.S. patent application Ser. No. 11/655,363, filed on Jan. 19, 2007, the disclosure of which is hereby incorporated herein by reference.
The devices at the edge of the SIA domain classify the interested traffic, placing the classification result inside of a shared SIA context, and then redirecting the tagged packet to the next hop service in the SIA service path. Each service hop in the path receives the packet, uses the shared context to identify the traffic classification, and applies the appropriate service policy associated with the SIA classification. After service application, it derives the next hop in the service path associated with the shared context in the packet and then sends the traffic to the next service node. The final service in the path removes the shared context from the packet and forwards the packet to the original destination.
A consideration in SIA path forwarding is to uniquely select the next service in a path in a generic way, without depending on any transport mechanism of the underlying platform. As the traffic classification id of the SIA context in the packet remains constant throughout the service path, it alone is not adequate for selecting the next service in the path for all topologies. Multiple services can be co-located in the same physical service hosting device, and the SIA packet may be seen multiple times by the SIA forwarding plane of the physical device. There is no information in the SIA context, as it is currently defined, that can be used by the data plane to determine the previous hop from which the packet is received to uniquely select the next service in path. Consequently, an SIA packet cannot be switched as desired in a service path, and may cause loops or forwarding ambiguities.
A generic solution for SIA data plane switching that addresses these looping and path ambiguity concerns would be desirable. It would be particularly desirable if such a solution were to leverage existing networking industry standards so that the hardware-based platforms do not require any ASIC re-spins.